Chief pilot Jim Payne is planning an ambitious mission for the glider.

He and a second pilot plan to soar between 90,000 and 100,000 feet in July 2016. That's higher than the U.S. spy planes U-2 and SR-71 and 40,000 feet higher than any human has reached in a glider.

It's also higher than any other piloted winged aircraft has flown in sustained flight. Balloons have floated higher, and experimental U.S. government "X-planes" have zoomed higher, but Perlan 2 will be up there for hours.

"At that height, stars are visible even during the day," Payne said. "It'll be a lot of fun, that's for sure."

From a base in Argentina near the Andes Mountains, the plane will be towed into the air by a powered aircraft. When Perlan 2 detaches from the tow plane, Payne and his co-pilot will be on their own for six to eight hours.

Getting to 90,000 feet will be tricky. The team plans to use the polar vortex and a related weather phenomenon called the stratospheric polar night jet to ascend higher and higher.

"As the wind comes over the mountains, it puts a wave in the air perpendicular to the mountains, like a rock puts a wave in a stream," Payne said.

The two seats built into Perlan 2's pressurized cockpit are about the size of recliner chairs.

"It's very comfortable," Payne said. "Flying these long missions, you're continuously analyzing what's going on around you: the weather, the wind currents, the air traffic control situation and so on, so time goes by pretty fast."

The plane has a wingspan of 84 feet, weighs 1,800 pounds and will hit a maximum speed of about 280 mph. At that speed, the glider's airspeed indicator will show only 36 knots (about 41 mph) because of the ultra-thin air at 90,000 feet.

In an emergency, Payne would pull a parachute that would quickly drop the plane to a lower altitude. Then, a recovery parachute would deploy, gently lowering Perlan 2 to the ground.

Scientific equipment aboard the aircraft will gather data to study weather and atmospheric phenomena. Engineers may use that information to learn more about how aircraft perform in very thin air.

Those lessons might contribute to the design of an aircraft that could fly on planets with ultra-thin atmospheres, such as Mars.